RAM has many functions, but its primary function is to store programs and drivers for the various system devices. It is probably the most important type of memory in your PC.
We will discuss three types of memory:
- RAM
- ROM
- Cache
Courtesy Kingston Technology Corp.When you enter a command from your keyboard, the CPU (microprocessor) processes the command and calls for data (a program or data file) to be copied from a storage device (hard disk, floppy, CD-ROM, etc.) into memory, where it is stored temporarily until the CPU needs it. The memory then provides the data to the CPU more quickly than from the storage device. This data may be a program and actual data. This bulk memory is called "RAM", and is what you are referring to when you say "my system has 8, 16, 32 MB of memory".
The RAM is divided into multiple parts (locations, not types):
- Conventional Memory (location 0 thru 640 KB)
- High (Upper) Memory (641 thru 1 MB)
- Extended Memory (addresses above 1 MB)
- Expanded Memory (sometimes).
RAM, itself, usually consists of Dynamic Random
Access Memory (DRAM). DRAM has several variations (such as FPM RAM, EDO RAM, and SDRAM)
of chips mounted on Single In-Line Memory Modules (SIMM)
boards or chips, or on Dual In-Lin memory modules. A single 30-pin SIMM can hold up to 4MB
and a 72-pin SIMM can hold up to 32 MB of memory. I think I am right in saying that a 168-pin
DIMM chip can contain up to 256MB of SDRAM.
Numerous "types" of memory exist and your specific PC may contain several types of memory for different purposes. Some of the terms you will hear are: RAM, DRAM, SRAM, EDORAM, SDRAM, ROM, PROM, EPROM, EEPROM, FLASH, internal and external cache, etc. These terms will be discussed below and in the "Terms and Definitions" selection.
Before I confuse you more, let me give you a table which will list these types and the normal uses for them:
| Memory Type | Use |
|---|---|
| ROM | BIOS, CMOS, Special function Chips. |
| RAM | Main Memory - FPM RAM, EDO & BEDO RAM, Synchronous DRAM (SDRAM) |
| DRAM | Chips on SIMM boards or Motherboard (Main Memory)-DRAM is actually FPM, EDO RAM, or SDRAM on a chip. |
| SRAM | Static RAM, used as External (L2)CACHE. L2 SRAM is on chips. L2 On-board cache is in the CPU chip. It comes in 3 basic types - Async SRAM, Sync SRAM, and PB SRAM (Pipelined Burst RAM - the fastest). |
| FPM | Fast Page Mode RAM used in 486 or before style motherboards. I think it is normally 30 pin SIMMs, but may also be on 72 pin SIMMs in some Intel Pentium based systems. The 70ns access time will work with the older, slower 486 CPUs, but for a system with bus speeds of 66MHz, you will need the 60ns speed SIMMs. |
| EDO RAM | Extended Data Out RAM Memory used on Pentium or later type motherboards. EDO RAM is not designed for 486 or earlier motherboards. EDO RAM is on 72-pin SIMMs. EDO RAM comes in plain EDO and Burst EDO (BEDO RAM) versions. EDO and BEDO RAM are ok in systems with bus speeds up to 66MHz. |
| SDRAM | Synchronous DRAM (Pentium w/MMX has SDRAM as main memory). SDRAM memory is on 168-pin DIMM chips. SDRAM comes in several types with speeds from 10, 15, 20, and 25 nanoseconds. |
| FLASH | Normally, it is memory on a card. The size of a PCMCIA card. |
Lets discuss some of them below. Click on the type of memory for a short discussion.
- Some of the types of memory are:
- RAM (Random Access Memory)
- ROM (Read Only Memory)
- Cache Memory
- Conventional, High, and Extended Memory
- Expanded Memory
- Flash Memory
HOW MUCH RAM MEMORY DO YOU NEED?
No one can say exactly - you need to know things about your system operating
system, the type of applications you will run on your PC (graphics, multi-media,
word processing, etc). Let me give you a few hints:
Just remember this: You can have all the RAM memory you can install; but,
if you do not have adequate internal and external cache, good video cards,
a 32-bit or 64-bit bus, etc., you will still operate somewhat slower.
What do you need to know before purchasing memory? .
Courtesy Kingston Technologies Corp.Quantity GENERAL USES
4 MB DOS applications, maybe Windows 3.1, a few old word
processing packages, etc.
8-12 MB Windows for Workgroups, small word-processing, E-Mail,
only a few (1 to 3) applications open. Maybe an Internet
package such as Internet Explorer or Netscape, AOL, etc. Will be
somewhat inefficient.
12-16 MB Windows for Workgroups, supposedly Windows 95 (not really!),
Word processing, E-Mail, WEB interfaces, FAX, spreadsheets, and
low level graphics applications. Few applications open
simultaneously.
16-24 MB You can now load Windows NT Server, Windows NT Workstation,
and Windows 95. NT Server works inefficiently at this level.
Some number crunching, spreadsheets, E-Mail, WEB browsers,
some graphics and audio-visual (but weak).
24-32 MB Now you can do heavy applications. Spread sheets,
statistical analysis programs, large databases, and multiple
applications open. Even a little graphics and games - a
an acceptable speed.
32-64 MB Starting into decent graphics, with word processing, page
layouts, even some good "audio visual" type applications.
64-128 You are now read for medium to high level graphics and
animation - if you have the other necessary hardware. Photo
editing, multimedia, word processing, illustration graphics,
the whole nine yards!
128+ MB Now you are talking! This is the level for efficient
Windows NT Servers with many users. Multimedia and about
everything else!
Buses